Figure 5. Glycerol IXS spectra, sound velocity and attenuation.

IXS spectra of glycerol liquid at 298 K measured at different momentum transfer Q=0.5 nm⁻¹ (a), Q=1 nm⁻¹ (b) and Q=1.4 nm⁻¹ (c), respectively. Dashed dark-blue lines are UHRIX resolution functions. Solid green lines are damped harmonic oscillator (DHO) functions convoluted with the resolution function. Solid red lines are a sum of the two, fitted to the experimental spectra. The dashed light-blue line in c is an IXS spectrum of glycerol measured with a conventional IXS spectrometer at Q=1.5 nm⁻¹ (ref. 31). The apparent sound velocity (d) and the reduced broadening Г_Q/Q² (e) of the acoustic-like modes, obtained from the least-squares fit of the experimental data to the DHO model, are shown with black circles and ±1σ error bars.